Its even worse when you force Firefox to use wayland its icon doesn’t even show.
Edit: Oh since everyone now is confused; I only have the flatpak version of Firefox installed yet it doesn’t use the pinned icon and doesn’t even use the firefox icon under wayland at all.
I don’t get it. Do you have two versions of Firefox installed?
Don’t know about the OP, but I only have one version installed. If I don’t have it open, a single icon shows on the task bar. If I press that icon, FF opens and a second icon shows up, that represents only the opened FF, while the original icon remains.